Gov. Cuomo’s humiliating dependence on Mayor de Blasio to win the endorsement Saturday of the leftist Working Families Party — whose pro-tax and anti-business stance Cuomo has claimed to be against — will be “a central theme’’ in Rob Astorino’s campaign against him through the fall, Astorino told The Post Sunday.

“The New York City political circus will now be coming to the rest of the state thanks to Andrew Cuomo, and that will definitely be a central theme in my campaign,’’ said Astorino, the Westchester County executive.

“The radicals that Cuomo is now in bed with are the greatest threat we have in New York right now,’’ Astorino continued.

“The Working Families Party is hellbent on driving up taxes and destroying businesses and the middle class. That’s the deal Andrew Cuomo has cut to try to save his political life.’’

Republican strategists expect the WFP’s endorsement to provide a significant boost to Astorino’s support in the heavily taxed and economically anxious suburbs, the key battleground in the Cuomo-Astorino contest.

“De Blasio and the WFP are the suburban voters’ worst nightmare: They represent higher taxes, hostility to business and union domination, all the things people go to the suburbs to escape,’’ said a prominent Astorino backer.

State GOP Chairman Ed Cox was gleeful over the union-controlled WFP’s Cuomo endorsement.

“By accepting the Working Families Party endorsement, Andrew Cuomo just sold his soul to Bill de Blasio and the radical New York City left,’’ said Cox.

“We already know that Andrew Cuomo’s election-year ads claiming that he is ‘pro-business’ and ‘bipartisan’ are nonsense, but this seals this deal.”

Cuomo was able to win the endorsement of the WFP only through de Blasio’s last-minute intervention.

Maverick Democrat Bill Samuels, who threatened to run against former US Rep. Kathy Hochul, Cuomo’s choice for lieutenant governor, said Sunday he won’t enter the race because of the WFP’s decision to back the Cuomo/Hochul ticket.

“I’m sorry, but standing there alone just doesn’t make any sense. It never entered my mind that the WFP would endorse Cuomo the way they did,’’ Samuels, a sharp Cuomo critic, told The Post.

Cuomo’s efforts to demonize Astorino in TV ads and Democratic Party attacks as “far-right,” “ultra-conservative’’ and a supporter of racially discriminating zoning laws are about to encounter a serious impediment: repeated praise for the Westchester County executive from Cuomo’s fellow Democrats.

Astorino’s campaign has assembled an impressive list of statements from powerful Democrats — ranging from former Gov. and current state Democratic Party Chairman David Paterson to US Sen. Charles Schumer and state Comp­troller Tom DiNapoli — that it will soon roll out to counter Cuomo’s efforts.